The invention relates to an arrangement for detecting a beginning of injection in a diesel internal-combustion engine.
Such an arrangement is already known from German Offenlegungsschrift 2,231,165. In it, an electric signal corresponding to the pressure in an injection line of a diesel internal-combustion engine is used to obtain a trigger signal for a stroboscope lamp. The signal is passed via a clamp circuit, for zeroing, to a trigger with fixed lower operating point, the output signal of which passes via a differential element for triggering of the stroboscope lamp. Furthermore, between the trigger and the differential element are connected a gate circuit and a monostable flip-flop, which actuates the gate circuit speed-dependently. Consequently, a multiple triggering of the stroboscope lamp, which could be caused by compressive oscillations is avoided.
Furthermore, a measuring device for determination of a dynamic beginning of feeding of diesel engines is known from the publication MTZ 1964, volume 7, page 292 et seq. Here too, the measuring device preferably serves for the triggering of a stroboscope lamp. The pressure detected in an injection line of the diesel internal-combustion engine is converted by a magnetostrictive transducer into a corresponding electric pressure signal, which is first differentiated and then passed to a switching stage, a output signal of which represents a trigger signal for the stroboscope lamp. To prevent multiple triggering of the stroboscope lamp, connected upstream of the switching stage is a gate stage, which actuates a gate stage (sic) by a monostable flip-flop.
However, such arrangements for detecting a beginning of injection are also used in injection controls for diesel internal-combustion engines, such as are known for example from U.S. Pat. No. 4,265,200. Such injection controls require the actual beginning of injection as actual parameter. Frequently, so-called pintle stroke transducers are used for this, which detect the movement of the pintle of the injection nozzle and thus the actual beginning of injection. As a result, the injection nozzle is of course made more complicated in design and thus more expensive, at the same time the space required for the injection nozzle becomes greater, since the pintle stroke transducer has to find space in the injection valve housing, together with its electrical connections. Because of these drawbacks, it is sometimes necessary to dispense with a pintle stroke transducer.